It is proposed: (1) To see if L-tartrate-inhibitable acid phosphatase of lysosomes is essential to the animal. (2) To see if the cytoplasmic tartrate-inhibitable phosphatases in animals have their origin in the lysosome and if the lysosomal phosphatases in the various tissues in an animal are products of the same cistron(s) and if and how the quantity and nature varies with tissue function, developmental stage, senescence, and conditions such as wasting diseases and cancer. (3) To seek the significance of the curious stereo-specific tartrate inhibition of a previous observation that all animal species tested from protozoa to man possess such an enzyme, whereas no higher plants or bacteria do, while it is scattered among the fungi. To these ends the following general approach is envisaged: 1) Antibodies to pure lysosomal phosphatase are to be administered to cells in culture and effects observed on growth rate, viability, enzyme activity, etc. L-tartrate or a suitable derivative will also be tested similarly. Antibodies will also be tested against the intact animal. 2) Identity of the enzymes from cytoplasm and lysosomes from various tissues will be isolated by specific tartrate-based affinity columns. 3) A correlation between the phylogenetic distribution with the suspected lysosomal distribution will be sought, using cytological evidence, enzyme latency and presence of other enzyme markers.